MINI on steel grating bridge: alignment question

[2nd Mini]

I occasionally drive my MINI back and forth over a steel draw bridge on an interstate highway. The surface is steel grating. One crosses the lift section at speed, as in 55-65mph. Going one way, the MINI heels around a little and feels a little insecure. Going the other way (North), the car slews around quite a bit and feels VERY insecure. Other than when the car is on the grating, even on grooved pavement, the MINI feels very solid, secure, and well-aligned. My other cars take this bridge with a little more grace, albiet maybe a tad slower... I've never really thought twice about it bridge with the other cars but the MINI wanders more like a motorcycle.

Here's the question: Should I suspect the alignment on the MINI or is this a "benefit" of the short wheelbase and tight suspension?

Hampton Roads folks, I'm speaking of the high-rise bridge on I-64 in Chesapeake.

Bob

[Super Dooper CooperS]

May be something to do with the reduced grip on the grid combined with the harder sidewall of the runflats? Just a suggestion....

[GordonD]

there was thread on this issue some months back which - if I rememeber correctly - concluded it was just a characteristic of run-flats i.e. stiff side walls and high pressure.

[chiph]

It's just the steel grating causing more tramlining than usual. The steel ridges in the direction of travel are seldom perfectly aligned, and they drop into the grooves of your tires, causing the unpleasant wandering feel as they push your car sideways.

I would expect the Dunlops to not do it as bad, as those tires don't have as many circumferential grooves.

I wonder why the effect doesn't cause the DSC to freak out? After all, the steering wheel is staying straight, but the car is moving back & forth.

Chip H.

[grumpy07470]

It gets real exciting on a motorcycle

[AprilWhine]

I've driven the high rise bridge, but I think the bridge to the downtown tunnel on 264 is also very exciting!

The wheelbase is similar on my Beetle, and both act about the same. The MINI has just a bit more drift.

[Rae]

Definitely the run-flats. Definitely definitely...

I hit one in CT coming back from New York and thought I was going to die, the car was wriggling so much. I changed tires (yokos) and went back the next weekend.. same bridge, same conditions weather-wise, WORLD of difference. No wiggle, just grins!

~Rachel